1. Field of the Invention
The invention relates to an eraser, composed of fillers, a thermoplastic material based on synthetic rubber as the binder and other additives.
2. Description of the Prior Art
In a known eraser of this type, as disclosed in Belgian Pat. No. 673,229, it is proposed to use polychloroprene, chlorosulfonated polyethylene, polybutadiene, polyacrylonitrile or polyisobutylene as the binder.
However, this eraser was found to be disadvantageous because an additional vulcanization process or a peroxidic crosslinking is required due to the selected binders. In addition, as a rule, softeners, such as, for example, chloroparaffins, which have a great tendency to migrate, are required.
In accordance with another proposal as disclosed in U.S. Pat. No. 3,738,951, a butadiene-styrene block polymer with a butadiene to styrene ratio of 4:1 to 1:1 (80:20 to 50:50%) is used as the binder. Furthermore, in this case, the use of a very high portion of factice and naphthenic oil is proposed as softeners.
Since factice as well as naphthenic oils are relatively expensive components, these known mixtures always result in relatively expensive final products.